1. Field of the Invention
The present invention relates to a process for extracting a substance or a substance group from a mixture, wherein the process utilizes a solvent for separation.
2. Description of the Related Art
A process of this type is known in the art as the extraction by means of a selective solvent, i.e., a solvent which either separates the substance or the substance group to be extracted or which leaves the substance or substance group to be extracted in the residue.
The efficiency of the extraction is frequently limited with respect to its selectivity because, when extracting the soluble substance or substances, molecules of other substances which are normally not soluble in the solvent under the adjusted conditions, are also taken into the solution; in addition, the differences in the solubility between the substances to be separated are already small from the outset.
The efficiency of the extraction is also limited because of the fact that it practically always only makes possible a separation between soluble substances and non-soluble substances.